The invention relates to a method for the electrolytic extraction of metal from a solution containing metal ions, wherein an anode is immersed into the solution in a first cell and metal is precipitated from the solution onto an electrode. This electrode is then transferred to a second cell containing a liquid electrolyte, and the precipitated metal is released again from the electrode into the electrolyte, and reprecipitated from the electrolyte onto a counter-electrode. The electrode freed of the metal is then transferred from the second cell back into the first cell. The invention also relates to an apparatus and an electrode for the practice of the method.
In German Patent Disclosure Document 22 32 903 a method is disclosed for the electrolytic refinement of copper from salt solutions thereof contaminated with other metal ions, using titanium electrodes as the electrolyte plates. The titanium electrodes are placed as cathodes in a first solution and, after precipitation of the copper, transferred to a second bath containing pure electrolyte where 100% of the previously separated copper is released again, while the titanium electrode is connected as the anode. Titanium is used as the material of the reversible electrode, and after the anodic release of the copper the electrode can be reused immediately in the first bath without any intermediate treatment, where it is connected as the cathode; when connected anodically the titanium electrode behaves like a copper anode as long as copper adheres to the titanium anode; the passivation of the titanium, which occurs after the removal of the copper, then manifests itself in a sharp drop in current and a sharp rise in voltage. Even though good use can be made of this spontaneous current drop and voltage rise for the automatic control of the electrolysis process, the possibility of largely automatic operation is substantially limited since the shutting off of the cathodically connected titanium electrode is not so easy to control; automatic operation is problematical because special manipulating tools are necessary for the transfer of the titanium plate to the particular solution.
Another method for the electrorefinement of a metal from the group, copper, zinc, nickel, lead or manganese, using a titanium electrode as cathode, is disclosed in GB Patent 1345411. The removal of the precipitated metal from the titanium electrode is performed in this case by mechanical stripping. In one embodiment the electrical series connection of a plurality of copper refinement cells is described, with the same current flowing through all of them; at the same time different cathode current densities can be achieved depending on the size of the cathode surfaces immersed in the electrolyte.